Scala--pack your Future[T]; Kotlin is coming!

A presentation to Outbrain developers

1. Scala--pack your Future[T] 
 Kotlin is coming! Ohad Shai Software Developer && Team Leader @ Outbrain
2. Disclaimer -- lifey
3. About Me • Developing Software since 2005 • Mainly in Java and JVM languages • Works on backend systems • Maintainer of kotlin-logging open-source lib • Kotlin advocate on my spare time since early in 2016
4. What’s wrong with Scala?
5. What’s wrong with Scala? • Readability sucks.
6. What’s wrong with Scala? • Readability sucks. Examples: – Collections  def map[B, That](f: A => B) (implicit bf: CanBuildFrom[Repr, B, That]): That
7. What’s wrong with Scala? • Readability sucks. Examples: – Collections – Implicit conversions
8. What’s wrong with Scala? • Readability sucks. Examples: – Collections – Implicit conversions – Operator overloading
9. What’s wrong with Scala? • Readability sucks. Examples: – Collections – Implicit conversions – Operator overloading – Underscore 
10. What’s wrong with Scala? • Scala has levels of features • There is more than one way to do it
11. What’s wrong with Scala? • Scala has levels of features • There is more than one way to do it • Readability sucks
12. What’s wrong with Scala? • Backward compatibility – “Scala isn’t binary compatible between minor versions.”
13. What’s wrong with Scala? • Compilation time > mvn clean install
 … [INFO] ApiTestSupport ........................................ SUCCESS [ 7.115 s]
 [INFO] AmplifyWafSim ......................................... SUCCESS [ 32.680 s]
 [INFO] Tracktor .............................................. SUCCESS [01:05 min]
 [INFO] AuthorizationSim ...................................... SUCCESS [ 1.080 s]
 [INFO] TracktorSim ........................................... SUCCESS [ 44.077 s]
 [INFO] BillingPocService ..................................... SUCCESS [ 1.234 s]
 [INFO] Shorty ................................................ SUCCESS [ 3.410 s]
 [INFO] Mushu ................................................. SUCCESS [ 26.661 s]
 [INFO] SpectorSim ............................................ SUCCESS [ 45.317 s]
 [INFO] WallStreetSim ......................................... SUCCESS [ 46.435 s]
 [INFO] AutoMarkerSim ......................................... SUCCESS [ 37.738 s]
 [INFO] BillingEngine ......................................... SUCCESS [ 14.198 s]
 [INFO] ------------------------------------------------------------------------
 [INFO] BUILD SUCCESS
 [INFO] ------------------------------------------------------------------------
 [INFO] Total time: 06:37 min (Wall Clock)
 [INFO] Finished at: 2017-07-02T15:13:48+03:00
 [INFO] Final Memory: 970M/2498M
 [INFO] ------------------------------------------------------------------------ >
14. What’s wrong with Scala? • Compilation time > mvn clean install | grep min 
 [INFO] AdminSite .......................................... SUCCESS [ 5.005 s]
 [INFO] www ................................................ SUCCESS [01:05 min]
 [INFO] AmeliaLib .......................................... SUCCESS [01:30 min]
 [INFO] EditorialAdminProxy ................................ SUCCESS [ 2.704 s]
 [INFO] EditorialAdmin ..................................... SUCCESS [ 38.963 s]
 [INFO] Amelia ............................................. SUCCESS [02:29 min]
 [INFO] AmeliaReports ...................................... SUCCESS [01:16 min]
 [INFO] AmplifyApp ......................................... SUCCESS [01:17 min]
 [INFO] Sandbox ............................................ SUCCESS [01:16 min]
 [INFO] PVACEngine ......................................... SUCCESS [01:25 min]
 [INFO] PlasticRex ......................................... SUCCESS [01:22 min]
 [INFO] AmeliaSim .......................................... SUCCESS [02:21 min]
 [INFO] AmeliaReportsSim ................................... SUCCESS [01:05 min]
 [INFO] GateKeeper ......................................... SUCCESS [01:23 min]
 [INFO] DataScienceScaldingRunner .......................... SUCCESS [01:15 min]
 [INFO] GateKeeperSim ...................................... SUCCESS [01:28 min]
 [INFO] EventorSim ......................................... SUCCESS [01:13 min]
 [INFO] MarkerSim .......................................... SUCCESS [01:11 min]
 [INFO] Tracktor ........................................... SUCCESS [01:05 min]
 [INFO] Total time: 06:37 min (Wall Clock) >
15. What’s wrong with Java?
16. What’s wrong with Java? • Not much, it is just old with lot of (extra) baggage
17. What’s wrong with Java? • Not much, it is just old with lot of (extra) baggage • Verbosity, Verbosity, Verbosity
18. What’s wrong with Java? • Not much, it is just old with lot of (extra) baggage • Verbosity, Verbosity, Verbosity • Velocity
19. Our problems so far • Scala • Readability • Backward compatibility • Compilation • Java • Not concise / Verbose • Velocity
20. What is Kotlin • Statically typed Programming Language • Multi-Platform (JVM first, JS and Native) • Open Source • Developed by Jetbrains since 2010 • Version 1.0 on Feb. 2016 • Official Android (Google) support since May 2017 https://medium.com/@octskyward/why-kotlin-is-my-next-programming-language-c25c001e26e3
21. Kotlin Features • Concise • Safe • Interoperable • Tool-friendly
22. Why Kotlin? • Scala – the good parts • Practical • Tools, support • Community • Google adopted it
23. Basics • No new keyword
24. Basics • No new keyword • No Checked exceptions ☺
25. Basics • No new keyword • No Checked exceptions ☺ • == is equals (and we have ===)
26. Basics • No new keyword • No Checked exceptions ☺ • == is equals (and we have ===) • No primitives
27. Basics • No new keyword • No Checked exceptions ☺ • == is equals (and we have ===) • No primitives • Arrays are invariant (but default to Lists)
28. Basics • No new keyword • No Checked exceptions ☺ • == is equals (and we have ===) • No primitives • Arrays are invariant (but default to Lists) • Semicolons are optional (so don’t)
29. Basics val hello: String = "hi" val world: String? = null
30. Basics val hello = "hi" val world: String? = null
31. Basics val hello = "hi" val world: String? = null
32. Basics val hello = "hi" var world: String? = null
33. Basics val hello = "hi" var world: String? = null
34. Basics Java public class Service { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } Kotlin class Service { var name: String? = null }
35. Basics Java public class Service { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } Kotlin class Service { var name: String? = null } val service = Service() println("Name is “ + service.name)
36. Basics Java public class Service { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } Kotlin class Service { var name: String? = null } val service = Service() println("Name is ${service.name}")
37. Basics Java public class Service { private String name; public String getName() { return name; } public void setName(String name) { this.name = name; } } Kotlin class Service { var name: String? = null } val service = Service() println("Name is ${service.name}")
38. Fun fun appendToName(service: Service, toAppend: String): String { return "${service.name}-$toAppend" }
39. Fun fun appendToName(service: Service, toAppend: String): String { return "${service.name}-$toAppend" }
40. Fun fun appendToName(service: Service, toAppend: String): String { return "${service.name}-$toAppend" } appendToName(service, "chidc2")
41. Fun fun appendToName(service: Service, toAppend: String): String { return "${service.name}-$toAppend" } appendToName(service = service, toAppend = "chidc2")
42. Fun fun appendToName(service: Service, toAppend: String): String { return "${service.name}-$toAppend" } ServiceUtils.appendToName(service, "chidc2")
43. Fun fun Service.appendToName(toAppend: String): String { return "${this.name}-$toAppend" } appendToName(service, "chidc2")
44. Fun fun Service.appendToName(toAppend: String): String { return "${this.name}-$toAppend" } service.appendToName("chidc2")
45. Fun fun Service.appendToName(toAppend: () -> String): String { return "${this.name}-${toAppend()}" } service.appendToName("chidc2")
46. Fun fun Service.appendToName(toAppend: () -> String): String { return "${this.name}-${toAppend()}" } service.appendToName({ “chidc2” })
47. Fun fun Service.appendToName(toAppend: () -> String): String { return "${this.name}-${toAppend()}" } service.appendToName { “chidc2” }
48. Nullable Types val world: String? = null println(world.toUpperCase()) // In Java you will get NPE // In Kotlin you will get compilation error
49. Nullable Types val world: String? = null if (world != null) { println(world.toUpperCase()) }
50. Nullable Types val world: String? = null println(world.toUpperCase())
51. Nullable Types val world: String? = null println(world?.toUpperCase())
52. Nullable Types val world: String? = null println(world?.toUpperCase())
53. Data Class data class Campaign(val id: Int, val name: String) // you will get: - toString() - equals() / hashCode() - copy()
54. When Expression when (object) { 1 -> "One" "Hello" -> "Greeting" is Long -> "Long" in 2..10 -> "obj is in the range" else -> "Unknown" }
55. Collections val fruits = listOf("banana", "avocado", "apple", "kiwi") fruits .filter { it.startsWith("a") } .sortedBy { it } .map { it.toUpperCase() } .forEach { println(it) }
56. Coroutines • Lightweight threads • Suspend-able computation • Writing imperative/blocking style • Executed ‘similar’ to callback style
57. Coroutines val time = measureTimeMillis { val one = async(CommonPool) { doSomethingUsefulOne() } val two = async(CommonPool) { doSomethingUsefulTwo() } println("The answer is ${one.await() + two.await()}”) } println("Completed in $time ms") The answer is 42 Completed in 1017 ms
58. Coroutines val jobs = List(100_000) { index -> async(CommonPool) { delay(1000L) index } } println( jobs.sumBy { it.await() } )
59. Last minute bullets • Backward compatibility • Compilation Time • Readability • Operator overloading • Underscore
60. Question? Like Kotlin? We’re hiring!
61. Thank You! @OhadShai